We describe a new synthetic approach to fabricate Ni/Cu nanocable arrays by co-depositing nickel and copper atoms into the pores of anodic alumina membranes and to fabricate Ni nanotube arrays by selectively etching the Cu cores from the Ni/Cu nanocable arrays. The formation of the Ni-shelled Ni/Cu nanocables is attributed to the Ni ions adsorbed on the pore walls by a chemical complexation through hydroxyl groups. By varying electrodepositon parameters in this technique, we can control the lengths of nanocables and nanotubes, the shell thickness of the nanocables, and the wall thickness and surface morphology of the nanotubes. 相似文献
A simple hydrothermal method has been developed for the one-step synthesis of copper-core/carbon-sheath nanocables in solution. The obtained nanostructures were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM), Raman, and UV-vis spectrum analysis. These copper@carbon nanocables formed through the hydrothermal reduction/carbonization in the presence of surfactant cetyltrimethylammonium bromide (CTAB) acting as the structure-directing agent by hydrothermal treatment. HRTEM and selected-area electron diffraction (SAED) indicate that the resulted Cu nanowires had the preferred [110] growth direction. The influence of the reaction temperature, reaction time, and pH on the final products was investigated in detail. The possible formation mechanism for copper-core/carbon-sheath nanocables was also proposed. Amorphous carbon nanotubes can be obtained by etching the copper core in the nanocables. 相似文献
An effective method was developed for generation of insulating tubular boron nitride (BN)-sheathed nanostructures. ZnS nanowires and multilayered Si-SiO2 nanowires were successfully sheathed with insulating tubular BN-forming nanocables. Both the semiconductor nanowire cores and the BN sheaths are crystalline with well-uniform morphologies. 相似文献
Properties of attached boron nitride (BN) nanotubes based on linking two zigzag nanotubes through a carboxylic (–(CO)O–) linker were investigated by performing density functional theory (DFT) calculations. The linking boron and nitrogen atoms at the edges of two zigzag BN nanotubes were linked to the –(C]O)O– linker to make possible the attachments of two BN nanotubes together. Total energies, energy gaps, dipole moments, linking bond lengths and angles, and quadrupole coupling constants were obtained for the optimized structures to determine the properties of the attached BN nanotubes. The results indicated that different properties could be seen for the investigated models based on their linking status. For quadrupole coupling constants, the most significant changes of parameters were observed for the linking atoms among the investigated models of attached BN nanotubes. 相似文献
DFT calculations were performed to investigation of the influence of doping three atoms of aluminum on the electronic properties of the (4,0) zigzag boron nitride nanotube (BNNT). Also, adsorption properties of nitrosamine (NA) and thionitrosamine (TNA) molecules as carcinogen agents onto BN and BAl3N nanotubes were studied. The results show that the B3AlN nanotube is the most energetically favorable candidates for adsorption of these molecules. Also, B(B3Al)NNT/TNA complexes are more stable than B(B3Al)NNT/NA complexes. The HOMO–LUMO gap, electronic chemical potential (μ), hardness (?), softness (S), the maximum amount of electronic charge (ΔNmax) and electrophilicity index (ω) for monomers and complexes in the gas and polar solvent phases were calculated. The results show that the conductivity and reactivity of BNNT increase by doping Al atoms instead of B atoms. Also, the interaction of NA and TNA molecules with BN and BAl3N nanotubes results in significant changes in the electronic properties of nanotubes. Based on the natural bond orbital (NBO) analysis, in all complexes charge transfer occurs from NA and TNA molecules to nanotubes. Theory of atoms in molecules (AIM) was applied to characterize the nature of interactions in nanotubes. It is predicted that, BN and B3AlN nanotubes can be used to as sensor for detection of NA and TNA molecules. 相似文献
High quality single crystals of an inorganic-organic hybrid, p-phenylenediammonium tetrachlorocuprate (pPDA:CuCl4), suitable for high-resolution X-ray data collection, have been crystallized. pPDA:CuCl4 crystallizes at special positions in the P21/c space group of the monoclinic crystal system with only halves of the moieties in the asymmetric part of the unit cell. This compound forms a hybrid structure consisting of separate inorganic anion and organic cation layers linked by weak N-H???Cl hydrogen bonds. The Cu atoms are located at the centers of symmetry and each of them is surrounded by six chlorine atoms thus forming a tetragonal bipyramid. Two pairs of the chlorine atoms form short Cu-Cl bonds (2.27964(4) and 2.29765(4) Å), whereas the third pair forms the longest Cu-Cl bond (2.90452(4) Å). Experimental and theoretical electron density distributions have been established. There is an excellent agreement between theoretical and experimental properties at bond critical points. The total charge of the organic cation is equal to +1.64 \( \overset{-}{\boldsymbol{e}} \) and is neutralized by the charge of the inorganic anion. The orbital population analysis of the copper 3d electrons and analysis of geometry of the tetrachlorocuprate have been performed and they clearly show presence of the Jahn-Teller effect. Comparison of some experimentally derived parameters such as area and linear density distribution with those calculated on the base of relations derived from literature shows that a longer series of experimental charge density investigations of the hybrid structures should be measured. It should allow for obtaining more reliable relations among different parameters for the hybrid structures with a strong predictive power of such relations. Analysis of residuals of measured intensities of reflections and those resulting from the refined model shows a serious underestimation of esds of measured reflections used in the refinement. 相似文献
Adsorption of transition atoms on a (8,0) zigzag single-walled boron nitride (BN) nanotube has been investigated using density-functional theory methods. Main focuses have been placed on configurations corresponding to the located minima of the adsorbates, the corresponding binding energies, and the modified electronic properties of the BN nanotubes due to the adsorbates. We have systemically studied a series of metal adsorbates including all 3d transition-metal elements (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) and two group-VIIIA transition-metal elements (Pd and Pt). We found that many transition-metal atoms can be chemically adsorbed on the outer surface of the BN nanotubes and that the adsorption process is typically exothermic. Upon adsorption, the binding energies of the Sc, Ti, Ni, Pd, and Pt atoms are relatively high (>1.0 eV), while those of V, Fe, and Co atoms are modest, ranging from 0.62 to 0.92 eV. Mn atom forms a weak bond with the BN nanotube, while Zn atom cannot be chemically adsorbed on the BN nanotube. In most cases, the adsorption of transition-metal atoms can induce certain impurity states within the band gap of the pristine BN nanotube, thereby reducing the band gap. Most metal-adsorbed BN nanotubes exhibit nonzero magnetic moments, contributed largely by the transition-metal atoms. 相似文献
Optimization of the hydrated Cu(II)(N7-guanine) structures revealed a number of minima on the potential energy surface. For selected structures, energy decompositions together with the determination of electronic properties (partial charges and electron spin densities) were performed. In the complexes of guanine with the bare copper cation and that with the monoaqua ligated cation, an electron transfer from guanine to Cu(II) was observed, resulting in a Cu(I)-guanine(+) type of complex. Conformers with two aqua ligands are borderline systems characterized by a Cu partial charge of +0.7e and a similar value of the spin density (0.6e) localized on guanine. When tetracoordination of copper was achieved, only then the prevailing electron spin density is unambiguously localized on copper. The energetic preference of diaqua-Cu-(N7,O6-guanine) over triaqua-Cu-(N7-guanine) was found for the four-coordinate structures. However, the energy difference between these two conformations decreases with the number of water molecules present in the systems, and in complexes with five water molecules this preference is preserved only at DeltaG level where thermal and entropy terms are included. 相似文献
Summary: Copper/poly(vinyl alcohol) (PVA) nanocables have been successfully obtained by electrospinning a PVA‐protected copper nanoparticle solution. The molar ratio of copper ions to PVA (in terms of VA repeating units) plays an important role in the formation of copper/PVA nanocables. The average diameter of the copper cores and PVA shells is about 100 and 400 nm, respectively. The structures of the copper/PVA nanocables are characterized by transmission electron microscopy (TEM) and their formation is confirmed by scanning electron microscopy (SEM).
Ion beam creates changes in the material along their track, not only embody the excellent properties but also tailor new materials. When the ions are implanted into the nanomaterials, they collide with the target atoms and interact through three different phenomena; electron collision, nuclear collision and charge exchange. In the present study, 1 MeV O5+ ions were implanted in copper nanowires of diameter 80 nm synthesized using template synthesis approach. Electrical and structural properties were recorded using Keithley 2400 series source meter and Rigaku X-ray diffractometer respectively, before and after the implantation. I–V characteristics showed the ohmic behavior with enhancement in conductivity of copper nanowires after implantation. No structural damage in the nanowires was revealed by XRD spectra. The work done can be viewed as a positive aspect of implantation in metallic nanowires especially in 80 nm diameter Cu nanowires and may be utilized to fabricate nanodevices. 相似文献
The morphology of CdSe/SiO(2) was manipulated from core-shell-structured nanoparticles to nanocables by using a chemical vapor deposition (CVD) process. The growth of nanocables, with cores no more than 20 nm in diameter, is initiated by the formation of core-shell nanoparticles with SiO(2) as matrix and CdSe clusters dispersed inside. After the subsequent vaporization of the SiO(2) matrix, the follow-up CdSe vapor crystallizes with the remaining CdSe clusters as nuclei to form CdSe nanowires as the furnace was cooled to 1200 degrees C. During the controlled cooling of the furnace, the SiO vapor re-deposits to sheathe the nanowires. The thickness of the shell and the diameter of core were successfully controlled. The photoluminescence measurements show that the CdSe/SiO(2) nanocables have strong visible-light emission bands located at 590 and 688 nm, which are attributed to the defects induced by SiO(2) sheaths nanowires and the quantum confinement effect of the CdSe, respectively. The UV/Vis absorption spectra of the naked CdSe nanowires further validate the above-mentioned quantum confinement effect. The deterministic growth of these nanocables is very important for the design of the nanodevices based on them. 相似文献
The structure of copper species, dispersed on nanostructured ceria(particles, rods and cubes), was analyzed by scanning transmission electron microscopy(STEM) and X-ray photoelectron spectroscopy(XPS). It was interestingly found that the density of surface oxygen vacancies(or defect sites), induced by the shape of ceria, determined the geometrical structure and the chemical state of copper species. Atomically dispersed species and monolayers containing few to tens of atoms were formed on ceria particles and rods owing to the enriched anchoring sites, but copper clusters/particles co-existed, together with the highly dispersed atoms and monolayers, on cubic ceria. The atomically dispersed copper sites and monolayers interacted strongly with ceria, involving a remarkable charge transfer from copper to ceria at their interfaces. The activity for the low-temperature watergas shift reaction of the Cu/CeO_2 catalysts was associated with the fraction of the positively-charged copper atoms, demonstrating that the active sites could be tuned by dispersing Cu species on shape-controlled ceria particles. 相似文献
The interface properties of c-BN/Cu composite play an important role in its application. In this work, we employed first-principles calculation to investigate the bonding properties and electronic characteristics of the c-BN(111)/Cu(111) interface. The adhesion properties, partial density of states (PDOS), charge density, and charge density difference of different interfaces were analyzed. The results show that the interface of B-termination “OT” stacking mode is the most stable one. The density of states at the c-BN(111)/Cu(111) interface is similar to that of c-BN bulk phase, indicating that the electronic states of the c-BN layer are not affected by the Cu atoms. The PDOS diagram shows that the 2p orbital of B atoms and the 2p orbital of N atoms are hybridized in the c-BN layer. Besides, 2p orbital of B(N) atoms and 3d orbital of Cu atoms are hybridized in the interface. The covalent bonds and ionic bonds in the interface of N-termination and B-termination OT stacking mode structures are stronger than that of “SL” and “TL” stacking mode. So, the OT stacking mode has larger adhesive energy. Furthermore, Cu and c-BN can form a good coherent interface, which can be used to prepare c-BN/Cu composites and functional materials with excellent mechanical properties. 相似文献
Decoration of nitrogen vacancies by oxygen atoms has been studied by near-edge X-ray absorption fine structure (NEXAFS) around B K-edge in several boron nitride (BN) structures, including bamboo-like and multi-walled BN nanotubes. Breaking of B-N bonds and formation of nitrogen vacancies under low-energy ion bombardment reduces oxidation resistance of BN structures and promotes an efficient oxygen-healing mechanism, in full agreement with some recent theoretical predictions. The formation of mixed O-B-N and B-O bonds is clearly identified by well-resolved peaks in NEXAFS spectra of excited boron atoms. 相似文献
Coaxial nanocables of gallium phosphide (GaP) core with three different-typed single and double shells (i.e., silicon oxide (SiO(x)), carbon (C), and SiO(x)/C) were exclusively synthesized by the chemical vapor deposition method. The GaP/SiO(x)) nanocables were directly grown on gold-deposited silicon substrates. Deposition of C on the GaP nanowires and GaP/SiO(x) nanocables produces the GaP/C and GaP/SiO(x)/C nanocables, respectively. The outer diameter of the nanocables is <50 nm. The thickness and crystallinity of the C outer layers were controllable by the growth conditions. X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectroscopy, and photoluminescence reveal that the outer layer formation reduces the surface defects of GaP nanowires. A great enhancement of the conductivity due to the C outer layers has been measured by the four-probe method. The growth process of these nanocables has been discussed on the basis of the vapor-liquid-solid mechanism. 相似文献